Electronic devices come in many shapes and sizes. One type of electronic device can be formed by mounting electronic device components on a substrate. Some substrates can be quite small, i.e. credit card-size or less, such that the resultant device formed thereon is itself quite small. There is generally, within the industry, an emphasis on decreasing overall device dimensions while increasing the overall performance and/or capabilities of a device. Such industry focus presents challenges regarding, among other things, providing a device package which is sufficient for its intended purpose and durable enough to withstand the abuses expected in the operating environment.
An electronic device 20 is shown in FIGS. 1 and 2. Device 20 includes a flexible circuit substrate 22 upon which various electronic components have been mounted. In the illustrated example, device 20 is configured as a battery-powered communication device which is suitable for use as an RF communication device. Accordingly, device 20 includes an antenna 24 supported over substrate 22, a thin-profile battery 26 (FIG. 1) mounted on the substrate, and an integrated circuitry chip 28 configured for RF operation. An exemplary device and/or chip is shown and described in U.S. patent application Ser. No. 08/705,043, which names James O'Toole, John R. Tuttle, Mark E. Tuttle, Tyler Lowrey, Kevin Devereaux, George Pax, Brian Higgins, Shu-Sun Yu, David Ovard and Robert Rotzoll as inventors, which was filed on Aug. 29, 1996, is assigned to the assignee of this patent application, and incorporated by reference herein.
One challenge in producing a device such as device 20 relates to mounting the electronic components on the substrate; in particular, mounting battery 26 suitably on substrate 22 such that not only are desirable electrical connections made between electronic componentry and the battery, but the battery is sufficiently physically fixed over the substrate so that it does not become inadvertently dislodged.
Referring to FIGS. 2 and 3, device 20 is shown prior to battery 26 being mounted thereon. Substrate 22 is shown in an intermediate state of assembly and includes a temporary carrier substrate 36 and a thin polyester substrate 38 bonded therewith. Dashed line 30 in FIG. 2 depicts an outer perimeter of battery 26 where it is to be mounted on the substrate. Shown generally at 32 and within perimeter 30 is a conductive contact node pattern which, heretofore, has been utilized to form an electrical and mechanical connection with a thin-profile battery such as battery 26. Typically, such electrical and mechanical connection is formed through the application of a suitable conductive epoxy over the pattern, with the battery being subsequently bonded into place. Specifically, and shown in FIG. 3, conductive epoxy 34 is formed over each of the depicted nodes (not specifically designated). Battery 26 (FIG. 4) is placed on the epoxy such that a suitable bond is formed between the battery and the nodes.
It is desirable in some instances to encapsulate electronic devices within a mass of encapsulating material. Referring to FIG. 5, an encapsulating material 40 is formed over the substrate including the electronic components and battery 26. One process which is useful for providing encapsulant material around the electronic components, including underneath battery 26, is to repetitively vacuum process the substrate such that the encapsulant material eventually flows to a position underneath battery 26. Specifically, once encapsulant material 40 is provided over battery 26 as shown, any air underneath the battery is typically entirely surrounded by the encapsulant material and hence trapped. By conducting a vacuum draw down (typically in a vacuum chamber), the air which is trapped underneath the battery will be drawn out through the encapsulant material. When the vacuum is released, ambient air will, in trying to return underneath the battery, exert pressure on the encapsulant material and thereby move it in a direction underneath the battery. Such should theoretically occur sufficiently to entirely fill the area underneath the battery. Yet, as shown in FIG. 6, this is not always the case.
Referring to FIG. 6, during vacuum processing, portions of the substrate can upwardly engage the battery and effectively block off the region beneath the battery. Such blocked-off area typically remains isolated during processing so that the encapsulant material does not sufficiently fill the area. In the illustrated example, substrate portions 42, 44 of polyester substrate portion 38 have been, through vacuum processing, deformed to engage the facing battery terminal housing member of battery 26. Such prevents encapsulating material 40 from achieving contact with battery 26 in areas designated with the letter "A". This condition is undesirable for a number of reasons including the inadequacy of encapsulating material coverage and the related impact it has on the ability of individual electronic components to be fully and rigidly supported over the substrate.
This invention arose out of concerns associated with providing improved apparatuses and methods for mounting electronic components over substrates. This invention also arose out of concerns associated with providing improved electronic devices.